LVDH wrote: ↑
Fri Sep 16, 2022 8:17 am
G-raph wrote: ↑
Thu Sep 15, 2022 8:45 pm
I think the pictures for JJR and Variante are from their first "rogue" CFD runs with the crazy numbers, wrong ground clearance and asymmetric results (as Matteo mentioned). It would be good to get these updated to the proper results, so we can compare everyone properly.
They are and I just fixed this, but you guys were faster than me....
Once again, thank you very much for these pictures, they are very interesting. I'm quite surprised and/or intrigued by some of them.
I'd be happy to comment them all, or answer any question anyone might have, but I understand that so early in the challenge this might not please everyone. Let me know what you think, but given where we are now it might be worth waiting for the Race 2 pictures anyway.
Maybe when we are closer to (or even after) the final race, it might also be useful to see the the same Cp_tot planes further upstream (using the larger scale), to see how the front-end has managed the wheel wake (X=0.533) and what the flowfield looks like under the floor before it enters the diffuser (X=2.967).
CAEdevice wrote: ↑
Fri Sep 16, 2022 9:27 am
I copy the link again for simplicity: https://mantiumchallenge.com/cfd-images ... mvrc-2022/
What do you think about? I appeal to professional aerodynamics. I consider Cp_Tot a bit like a measure of the amount of energy present in the fluid: is it better to have still energized air to come out of the diffuser or not?
You are right, Cp_tot IS a direct measure of the amount of energy present in the fluid.
The honest answer to your question is "it depends". Sorry, I wish there was a simpler solution too!
Ideally, you would have a lot of energy at the back of the diffuser to maximise the space the underfloor massflow can expand into. Think of any very low Cp_tot region as a wall that is blocking massflow at the back of your car, because this is stagnant flow with very low or even 0 velocity.
Having said that, to generate downforce you usually have to spend some energy creating vortices and accelerating the flow under your car surface. So having very clean flow at the back of the diffuser usually means you haven't generated much downforce along the way.
In my experience I would go with something like PurePowerRacing (or myself), but obviously none of us are on the podium. The winner has clearly worked the flow very hard.
The real question is : can you justify all the losses that you have created? Do they come from (for example) a very strong vortex that has genreated very low static pressure under your floor (as suggested by DynamicFlow in his post above)? Or is it just a useless flow separation that is only harming the exit condition at the back of the car (like at the junction between my rear wing and its endplate)?